In this newsletter edition the IMAGE research group is pleased to share study results from two of our recently published articles. Our first study reports on how fat mass and muscle mass relate to aging gracefully and the second study reports bone mineral density changes in male cyclists.

For access to more of the IMAGE group’s research publications visit: www.uchsc.edu/image. Click on “Faculty” and then select a faculty member. Click on “Pubmed Publications” to view each researcher’s recently published abstracts.

Study of Fat, Muscle, and Aging:

As people get older they gain fat and lose muscle. Excess fat mass (adiposity) and low muscle mass both increase the difficulty of performing certain tasks, such as going up stairs, getting up from a chair, or walking long distances. We conducted a study to answer the question: “What makes physical tasks more difficult: too much fat or too little muscle?”

We measured physical function in 109 women and men aged 60 to 84 years. Everyone was able to walk and had stable health. We measured physical function using the “CS-PFP” test. It includes everyday tasks such as carrying grocery bags and climbing stairs. We also asked the participants to complete a questionnaire on their perceived ability to do everyday tasks. Fat and muscle mass were measured using DXA, the same test that we use to determine bone density.

We found that fat mass was a better predictor of both measured and perceived physical function than muscle mass. In other words, having more muscle mass does not adequately compensate for having a high fat mass. We also found that men had better measured physical function than women. The findings do not mean that muscle mass is not important for completing everyday tasks. Rather, the study demonstrated that older adults, and particularly women, should strive to both minimize increases in fat mass and preserve muscle mass to maintain a good level of physical function. Perhaps, in the future, we will run a study to determine if the loss of fat mass through exercise improves physical function. Meanwhile – stay as active as you can!

The above full study article can be found in the journal, Obesity, Feb 21 2008. “Relative Contributions of Adiposity and Muscularity to Physical Function in Community-dwelling Older Adults”. Authors: Catherine M. Jankowski, Wendolyn S. Gozansky, Rachael E. Van Pelt, Margaret L. Schenkman, Pamela Wolfe, Robert S. Schwartz, and Wendy M. Kohrt.

Bone Density in Male Cyclists Study:

Is all exercise beneficial to bone health? Maybe not. A number of studies have found that endurance athletes, especially cyclists, are at risk for having low bone mineral density (BMD). However, it was not known if participating in endurance sports caused bone density to decrease or if the athletes who succeed in these sports are those who have a lighter, less dense skeleton to start.

The IMAGE research group recently enrolled 20 male road bike racers into a year-long study of their BMD. Consistent with previous studies, seven of the participants had BMD values lower than expected for healthy young men at the beginning of the study. This first prospective study of male cyclists found that BMD at the hip and various hip subregions (femoral neck, shaft, and trochanter) decreased over the course of the year of training and competition. There was also a strong trend towards a decrease in lumbar spine BMD. The cause of this decrease in BMD is unknown. Possible mechanisms include calcium loss through sweating, changes in sex or stress hormones, increased inflammation, or the absence of significant stress on the skeleton. The IMAGE research group is conducting other studies to examine these mechanisms and determine if there is a way to prevent this loss of bone.

Riding a bike is a weight-supported activity as opposed to a weight-bearing activity. As a result, it doesn’t place as much stress on the skeleton as activities like running or weight lifting. Current guidelines for exercise and bone health recommend engaging in weight-bearing activities (e.g. jogging, jumping, stepping) and weight lifting several times a week. The stresses to the skeleton from these activities typically cause bone to adapt by increasing or maintaining BMD. Those looking to preserve or improve their bone density should participate regularly in weight-bearing and resistance exercises.

The above full study article can be found in the Journal of Bone and Mineral Research, April 23 2008. “BMD decreases over the course of a year in competitive male cyclists.” Authors: Daniel W. Barry and Wendy M. Kohrt.

• The MOXI Study is examining how the use of ibuprofen in older, exercising women and men affects muscle and bone health. Eligible participants are 60-75 years of age who are not currently in a weight lifting program, have no history of peptic ulcers or stomach bleeding, and do not typically use acetaminophen, ibuprofen, or similar drugs more than 3 days per month. (COMIRB #06-0769)
• The DRIFT study is comparing the effect of two different diet methods - a normal, low calorie diet or intermittent fasting (not eating or drinking anything with calories every other day) - on weight loss and other health measures. Eligible participants are women and men, 18-55 years, who are obese based on a body mass index (BMI) ≥30 (to determine your BMI go to www.nhlbisupport.com/bmi). (COMIRB # 06-0383)
• The Lose-It Study will investigate the amount of exercise that health care providers should prescribe in order for patients to maintain weight loss. Eligible participants are healthy men and women between 18-45 years of age. Participants must be willing to engage in lifestyle changes including diet modifications and up to 100 minutes of daily physical activity. (COMIRB # 06-0369)

• The POWER Study is examining the role of the female sex hormone estrogen in preventing excess fat gain in women. Eligible participants are healthy women aged 20-40, who have regular menstrual cycles, and are not currently using hormonal contraceptives. (COMIRB #06-0512)
• The FLARE Study is examining how leg and hip liposuction surgery affects fat metabolism and cardiovascular health. Eligible participants are healthy pre- or postmenopausal women aged 40-55 years who are good candidates for leg and hip liposuction surgery and not using oral contraceptives or hormone therapy. (COMIRB #07-0339)
• The SHAPE study is examining how short-term changes in estrogen affect cardiovascular health. Eligible participants are premenopausal women 21-35, perimenopausal women 40-55, and postmenopausal women 45-70 years, who are non-smokers, have normal blood pressure, and who are not taking birth control or hormone therapy. (COMIRB # 06-0537)

• The MUSE study is investigating the effects of estrogen on changes in muscle due to lack of use. Eligible participants are women aged 21-40, who have regular menstrual cycles, are not currently using hormonal contraceptives, are physically active but not competitive athletes, and willing to wear a knee brace and use crutches for 9 days. (COMIRB #07-0379)

• The TEAM study is examining the effects of testosterone supplementation and exercise in men who have low-normal testosterone levels. Eligible participants are men, 60 years and older, non-smokers, in good general health, and not currently doing high-intensity weight lifting exercise. (COMIRB # 02-1056)
• The Mr. ACET study is examining how the use of acetaminophen and ibuprofen in older, exercising men, affects muscle and bone health. Eligible participants are men, 60 years and older, who are not currently in a weight lifting program, have no history of peptic ulcers or stomach bleeding, and do not typically use acetaminophen, ibuprofen, or similar drugs more than 3 days per month. (COMIRB # 06-0343)
• The PROXI study is determining if weight lifting helps to prevent the loss of muscle and bone mass that occurs in men with prostate cancer on androgen deprivation therapy (ADT). Eligible participants are men, 45-85 years, with prostate cancer, who are taking ADT or plan to start ADT. (COMIRB #02-958)
• The Kinetics study is examining the ability of leg muscles to use oxygen during exercise in healthy men and men with peripheral arterial disease. Eligible participants are non-smoking men, 50-70 years of age. (COMIRB #05-0718)